5-AMINO-2,4-DIHYDROXYBENZOIC ACID synthesis

Yield:69938-56-3 63%

Reaction Conditions:

Stage #1: 2,4-dihydroxy-5-nitrobenzoic acidwith hydrazine hydrate;palladium on activated charcoal in ethanol; for 4 h;Reflux;
Stage #2: with hydrogenchloride;tin(ll) chloride in ethanol;water; for 6 h;

Steps:

1; 2-6

In a 250 mL four-necked flask equipped with a thermometer and a spherical condenser, 4 g of 5-nitro-2,4-dihydroxybenzoic acid, 0.28 g of Pd / C catalyst, and 60 mL of ethanol were added in a dropwise manner using a constant pressure dropping funnel. 7mL of hydrazine hydrate, heated to reflux temperature, reacted for 4h, stopped heating, filtered the reaction solution while it was hot, and filtered the filtrate into an ice-water bath to cool down for 30min. Add 0.1g of stannous chloride, then add 100mL of concentrated hydrochloric acid, and let stand for 6h , Filtered, and the filter cake was dried to obtain an off-white product. The mass fraction by HPLC analysis was 94.83%, and the yield based on 5-nitro-2,4-dihydroxybenzoic acid was 66.12%.

References:

CN110396052,2019,A Location in patent:Paragraph 0033; 0041-0044; 0048; 0051-0052; 0055-0056